Why reading speed is low on my wd 2tb green HD drive?

I run a small business and I always use a hard drive for myworks and storing of the data. Some time I face the same problem that you arefacing right now. We always connect our hard drive with lots of externaldevices. Some external devices has got the genuine antivirus but some have notand they corrupt the files of hard drive of the laptop by the viruses due towhich data transferring speed decreases on the hard drive. So for that you mustupdate your own antivirus on your laptop and perform the full scan of the harddrive, check if a virus found if yes than it is causing due to the virus if nothan it may be causing due to corrupt or unauthorized data for that you canperform the formatting of your whole hard drive. I think that by the end ofthese all your problem will be removed completely and your laptop will neverhang in the future. It was really fun to help you.